Lignocellulosic Biomass as a Substrate for Oleaginous Microorganisms: A Review

Abstract

Microorganisms capable of accumulating lipids in high percentages, known as oleaginous microorganisms, have been widely studied as an alternative for producing oleochemicals and biofuels. Microbial lipid, so-called Single Cell Oil (SCO), production depends on several growth parameters, including the nature of the carbon substrate, which must be efficiently taken up and converted into storage lipid. Οn the other hand, substrates considered for large scale applications must be abundant and of low acquisition cost. Among others, lignocellulosic biomass is a promising renewable substrate containing high percentages of assimilable sugars (hexoses and pentoses). However, it is also highly recalcitrant, and therefore it requires specific pretreatments in order to release its assimilable components. The main drawback of lignocellulose pretreatment is the generation of several by-products that can inhibit the microbial metabolism. In this review, we discuss the main aspects related to the cultivation of oleaginous microorganisms using lignocellulosic biomass as substrate, hoping to contribute to the development of a sustainable process for SCO production in the near future.

Current Pretreatment/Cell Disruption and Extraction Methods Used to Improve Intracellular Lipid Recovery from Oleaginous Yeasts

“…Thus, a suitable strategy must be implemented to cater the problems from the oil production processes whilst minimizing the cost [46,47]. Among others, total production cost can be reduced by utilizing renewable feedstocks such as low-cost lignocellulosic materials and other industrial residues (containing high percentages of assimilable sugars) as fermentation substrates [48,49]. However, in an absence of cellulolytic activity in yeasts, free sugars are required to be released out from lignocellulosic materials through a pretreatment method (i.e., acid, base [50] or enzymatic hydrolysis [51]) before they can be converted into lipids by oleaginous yeasts.…”

The Potential of Single-Cell Oils Derived From Filamentous Fungi as Alternative Feedstock Sources for Biodiesel Production

“…Microbial lipid production from low-cost lignocellulosic and agro-waste material is a promising avenue ( Jin et al, 2015 ), however, these substrates are recalcitrant, and require a pretreatment step (e.g., steam explosion) before they can be hydrolyzed and fermented. During this process, various inhibitory by-products such as organic acids, phenolic compounds and sugar degradation products are generated, which may negatively affect microbial growth ( Yang et al, 2011 ; Zhao et al, 2017 ; Valdés et al, 2020 ). The advantage of using filamentous fungi is that they exhibit higher tolerance to these inhibitory by-products ( Abghari and Chen, 2014 ; Zhao et al, 2017 ).…”

Utilization of Biomass Derived from Cyanobacteria-Based Agro-Industrial Wastewater Treatment and Raisin Residue Extract for Bioethanol Production

“…Biomass is a promising renewable resource that can be used to generate different types of biofuels, including bioethanol. However, the use of biomass obtained from solid agricultural wastes increases fuel production cost due to its high lignin content that affects the saccharification process [1]. In contrast, many photosynthetic microorganisms (microalgae and cyanobacteria) have high a content of starch and cellulose and therefore constitute excellent substrates for bioethanol production [2][3][4] (Table 1).…”